GB1093134A - Nuclear reactor - Google Patents

Abstract

1,093,134. Fuel elements. GESELLSCHAFT FUER KERNFORSCHUNG m.b.H. July 28, 1965 [Aug. 1, 1964], No. 32226/65. Heading G6C. A cluster-type fuel element with spacers arranged at various levels between the fuel rods and attached to the can of at least one of the adjacent fuel rods has the fuel rods uniformly distributed but containing different mixtures of fissile and fertile material, the spacers being connected only with those fuel rods containing a relatively high percentage of fertile material. In one such element, as shown in Fig. 1, the fuel rods 1, 2 are assembled in a square basic lattice and surrounded by a can 4. The fuel rods 1, which contain a relatively high proportion of fertile material, are located at the intersections of a second lattice of twice the spacing of the basic lattice and have groups of four tubular spacers 3 attached at various points along their length. Longitudinal fins 5 or further tubular spacers 6 space the outermost fuel rods 2 from the can 4. In order to minimize the flow resistance of the spacers, they may be chamfered at their ends to give a trapezoidal longitudinal cross-section and joined by their longest sides to the fuel rods 1 (Fig. 3, not shown). Since their lines of contact with the fuel rods 2 are relatively short, this arrangement results in less disturbance of the heat removal from the highly loaded surfaces of the rods 2. The chamfered ends reduce the surface area contacted by the coolant resulting in a reduced flow resistance. Alternatively (Fig. 4, not shown), the walls of the tubular spacers taper to a point so as to minimize flow resistance and bulges on the outer walls of the spacers make point contact with the adjacent fuel rods 2. In the arrangement of the fuel rods shown in Fig. 5, fertile rods 11 bearing spacers 13 extend only throughout the core proper 14 of the reactor while the ends of the fissile rods 12 are connected to fertile rods 15 of large diameter. The diameter of the rods 15 may be such that they contact one another. Because there are no rods 11 in the blanket regions of the reactor, the coolant flow cross-sections at the inlet and outlet are still sufficient, even in this extreme case. The rods 12 have connections with the rods 15 which are permeable to gas and thus the large quantities of fission gases generated in the rods 12 are able to flow into the rods 15. Additional gas storage containers may be connected to the rods 15. It is possible to use other spacers of different shapes to those described, e.g. spacers made of sheet metal strips.